Debug Azure IoT Edge modules using Visual Studio Code

Article
2025-05-08

Applies to: IoT Edge 1.5

Important

IoT Edge 1.5 LTS is the supported release. IoT Edge 1.4 LTS is end of life as of November 12, 2024. If you are on an earlier release, see Update IoT Edge.

This article explains how to use Visual Studio Code to debug IoT Edge modules in multiple languages. On your development computer, use Visual Studio Code to attach and debug your module in a local or remote module container.

This article includes steps for two IoT Edge development tools.

Azure IoT Edge Dev Tool command-line tool (CLI). This tool is preferred for development.
Azure IoT Edge tools for Visual Studio Code extension. The extension is in maintenance mode.

Select the tool version using the tool selector button at the beginning of this article.

Visual Studio Code supports writing IoT Edge modules in the following programming languages:

C# and C# Azure Functions
C
Python
Node.js
Java

Azure IoT Edge works with these device architectures:

AMD64
ARM32v7
ARM64

For more information about supported operating systems, languages, and architectures, see Language and architecture support.

When using the Visual Studio Code IoT Edge extension, you can also launch and debug your module code in the IoT Edge Simulator.

You can also use a Windows development computer and debug modules in a Linux container using IoT Edge for Linux on Windows (EFLOW). For more information about using EFLOW for developing modules, see Tutorial: Develop IoT Edge modules with Linux containers using IoT Edge for Linux on Windows.

If you're new to the debugging capabilities of Visual Studio Code, see Visual Studio Code debugging.

Prerequisites

You can use a computer or a virtual machine running Windows, macOS, or Linux as your development machine. On Windows computers, you can develop either Windows or Linux modules. To develop Linux modules, use a Windows computer that meets the requirements for Docker Desktop.

To install the required tools for development and debugging, complete the Develop Azure IoT Edge modules using Visual Studio Code tutorial.

Install Visual Studio Code.

Add these extensions:

Azure IoT Edge extension. The Azure IoT Edge tools for Visual Studio Code extension is in maintenance mode.
Azure IoT Hub extension.

To debug your module on a device, you'll need:

An active IoT Hub with at least one IoT Edge device.
A physical IoT Edge device or a virtual device. Create a virtual device in Azure by following the steps in the quickstart for Linux.
A custom IoT Edge module. To create a custom module, follow the steps in the Develop Azure IoT Edge modules using Visual Studio Code tutorial.

Debug without a container using the IoT Edge simulator

The IoT Edge Simulator is a tool that runs on your development computer and simulates the behavior of a single IoT Edge device. You can use the IoT Edge Simulator to develop and test your IoT Edge modules without a physical device or a full IoT Edge device runtime.

The following debugging steps assume you have already created a custom module. If you haven't created a custom module, follow the steps in the Develop Azure IoT Edge modules using Visual Studio Code tutorial.

Debugging a module without a container isn't available when using C or Python.

Your module requires use of a ModuleClient object in the default module code so that it can start, run, and route messages. You'll also use the default input channel input1 to take action when the module receives messages.

Set up IoT Edge simulator

IoT Edge modules need an IoT Edge environment to run and debug. You can use an IoT Edge simulator on your development machine instead of running the full IoT Edge security subsystem and runtime. You can either simulate a device to debug solutions with multiple modules, or simulate a single module application.

Option 1: Simulate an IoT Edge solution:

In the Explorer tab on the left side, expand the Azure IoT Hub section. Right-click on your IoT Edge device ID, and then select Setup IoT Edge Simulator to start the simulator with the device connection string.
You can see the IoT Edge Simulator has been successfully set up by reading the progress detail in the integrated terminal.

Option 2: Simulate a single IoT Edge module:

In the Visual Studio Code command palette, run the command Azure IoT Edge: Start IoT Edge Hub Simulator for Single Module.
Provide the names of any inputs that you want to test with your module. If you're using the default sample code, use the value input1.
The command triggers the iotedgehubdev CLI and then starts the IoT Edge simulator and a testing utility module container. You can see the output similar to the following in the integrated terminal if the simulator is started in single module mode successfully. The output includes an example curl command to send a message to the simulator. You'll use the curl command later.
```
D:\Workspaces\EdgeSolution>iotedgehubdev start -i "input1"
...
```
You can use the Docker Explorer view in Visual Studio Code to see the module's running status.

The edgeHubDev container is the core of the local IoT Edge simulator. It can run on your development machine without the IoT Edge security daemon and provides environment settings for your native module app or module containers. The input container exposes REST APIs to help bridge messages to the target input channel on your module.

Debug module in launch mode

After the simulator is started successfully, you can debug your module code.

Prepare your environment for debugging, set a breakpoint in your module, and select the debug configuration to use.

In the Visual Studio Code integrated terminal, change the directory to the <your module name> folder, and then run the following command to build the .NET Core application.

dotnet build

If using the tutorial sample module, open the file ModuleBackgroundService.cs and add a breakpoint.

Go to the Visual Studio Code Debug view by selecting the debug icon from the menu on the left or by typing Ctrl+Shift+D. Select the debug configuration <your module name> Local Debug (.NET Core) from the dropdown.

Note

If your .NET Core TargetFramework is not consistent with your program path in launch.json, you'll need to manually update the program path in launch.json to match the TargetFramework in your .csproj file so that Visual Studio Code can successfully launch this program.

Select Start Debugging or press F5 to start the debug session.
In the Visual Studio Code integrated terminal, run the following command to send a Hello World message to your module. This is the command shown in previous steps when you set up IoT Edge simulator.
```
curl --header "Content-Type: application/json" --request POST --data '{"inputName": "input1","data":"hello world"}' http://localhost:53000/api/v1/messages
```
Note

If you are using Windows, making sure the shell of your Visual Studio Code integrated terminal is Git Bash or WSL Bash. You cannot run the curl command from a PowerShell or command prompt.
In the Visual Studio Code Debug view, you'll see the variables in the left panel.
To stop your debugging session, select the Stop button or press Shift + F5, and then run Azure IoT Edge: Stop IoT Edge Simulator in the command palette to stop the simulator and clean up.

Set up IoT Edge simulator

Option 1: Simulate an IoT Edge solution:

In the Explorer tab on the left side, expand the Azure IoT Hub section. Right-click on your IoT Edge device ID, and then select Setup IoT Edge Simulator to start the simulator with the device connection string.
You can see the IoT Edge Simulator has been successfully set up by reading the progress detail in the integrated terminal.

Option 2: Simulate a single IoT Edge module:

In the Visual Studio Code command palette, run the command Azure IoT Edge: Start IoT Edge Hub Simulator for Single Module.
Provide the names of any inputs that you want to test with your module. If you're using the default sample code, use the value input1.
The command triggers the iotedgehubdev CLI and then starts the IoT Edge simulator and a testing utility module container. You can see the output similar to the following in the integrated terminal if the simulator is started in single module mode successfully. The output includes an example curl command to send a message to the simulator. You'll use the curl command later.
```
D:\Workspaces\EdgeSolution>iotedgehubdev start -i "input1"
...
```
You can use the Docker Explorer view in Visual Studio Code to see the module's running status.

The edgeHubDev container is the core of the local IoT Edge simulator. It can run on your development machine without the IoT Edge security daemon and provides environment settings for your native module app or module containers. The input container exposes REST APIs to help bridge messages to the target input channel on your module.

Debug module in launch mode

After the simulator is started successfully, you can debug your module code.

Prepare your environment for debugging, set a breakpoint in your module, and select the debug configuration to use.

Add a breakpoint in your Java code.

Navigate to the Visual Studio Code Debug view by selecting the debug icon from the menu on the left or by typing Ctrl+Shift+D. Select the debug configuration <your module name> Local Debug (Java) from the dropdown.

Select Start Debugging or press F5 to start the debug session.
In the Visual Studio Code integrated terminal, run the following command to send a Hello World message to your module. This is the command shown in previous steps when you set up IoT Edge simulator.
```
curl --header "Content-Type: application/json" --request POST --data '{"inputName": "input1","data":"hello world"}' http://localhost:53000/api/v1/messages
```
Note

If you are using Windows, making sure the shell of your Visual Studio Code integrated terminal is Git Bash or WSL Bash. You cannot run the curl command from a PowerShell or command prompt.
In the Visual Studio Code Debug view, you'll see the variables in the left panel.
To stop your debugging session, select the Stop button or press Shift + F5, and then run Azure IoT Edge: Stop IoT Edge Simulator in the command palette to stop the simulator and clean up.

Set up IoT Edge simulator

Option 1: Simulate an IoT Edge solution:

In the Explorer tab on the left side, expand the Azure IoT Hub section. Right-click on your IoT Edge device ID, and then select Setup IoT Edge Simulator to start the simulator with the device connection string.
You can see the IoT Edge Simulator has been successfully set up by reading the progress detail in the integrated terminal.

Option 2: Simulate a single IoT Edge module:

In the Visual Studio Code command palette, run the command Azure IoT Edge: Start IoT Edge Hub Simulator for Single Module.
Provide the names of any inputs that you want to test with your module. If you're using the default sample code, use the value input1.
The command triggers the iotedgehubdev CLI and then starts the IoT Edge simulator and a testing utility module container. You can see the output similar to the following in the integrated terminal if the simulator is started in single module mode successfully. The output includes an example curl command to send a message to the simulator. You'll use the curl command later.
```
D:\Workspaces\EdgeSolution>iotedgehubdev start -i "input1"
...
```
You can use the Docker Explorer view in Visual Studio Code to see the module's running status.

The edgeHubDev container is the core of the local IoT Edge simulator. It can run on your development machine without the IoT Edge security daemon and provides environment settings for your native module app or module containers. The input container exposes REST APIs to help bridge messages to the target input channel on your module.

Debug module in launch mode

After the simulator is started successfully, you can debug your module code.

Prepare your environment for debugging, set a breakpoint in your module, and select the debug configuration to use.

In the Visual Studio Code integrated terminal, change the directory to the <your module name> folder, and then run the following command to install Node packages:

npm install

Add a breakpoint to your Node.js code.

Select Start Debugging or press F5 to start the debug session.
In the Visual Studio Code integrated terminal, run the following command to send a Hello World message to your module. This is the command shown in previous steps when you set up IoT Edge simulator.
```
curl --header "Content-Type: application/json" --request POST --data '{"inputName": "input1","data":"hello world"}' http://localhost:53000/api/v1/messages
```
Note

If you are using Windows, making sure the shell of your Visual Studio Code integrated terminal is Git Bash or WSL Bash. You cannot run the curl command from a PowerShell or command prompt.
In the Visual Studio Code Debug view, you'll see the variables in the left panel.
To stop your debugging session, select the Stop button or press Shift + F5, and then run Azure IoT Edge: Stop IoT Edge Simulator in the command palette to stop the simulator and clean up.

Debug in attach mode using IoT Edge simulator

C / Python
C# / Azure Functions / Node.js / Java

Debugging in attach mode isn't available for C or Python.

Debugging in attach mode is supported only in the following cases:

C# modules, including modules for Azure Functions, support debugging in Linux amd64 containers
Node.js modules support debugging in Linux amd64 and arm32v7 containers, and Windows amd64 containers
Java modules support debugging in Linux amd64 and arm32v7 containers

Tip

You can switch among options for the default platform for your IoT Edge solution by clicking the item in the Visual Studio Code status bar.

Set up IoT Edge simulator for IoT Edge solution

Start an IoT Edge simulator on your development machine instead of installing the IoT Edge security daemon to run your IoT Edge solution.

In the Explorer tab on the left side, expand the Azure IoT Hub section. Right-click on your IoT Edge device ID, and then select Setup IoT Edge Simulator to start the simulator with the device connection string.
Check the progress details in the integrated terminal to confirm the IoT Edge Simulator is set up successfully.

Build and run container for debugging and debug in attach mode

Open your module file and add a breakpoint.
In the Visual Studio Code Explorer view, right-click the deployment.debug.template.json file for your solution and then select Build and Run IoT Edge solution in Simulator. You can watch all the module container logs in the same window. You can also navigate to the Docker view to watch container status.
Go to the Visual Studio Code Debug view and select the debug configuration file for your module. The debug option name should be similar to <your module name> Remote Debug
Select Start Debugging or press F5, and then select the process to attach to.
In Visual Studio Code Debug view, you see the variables in the left panel.
To stop the debugging session, first select the Stop button or press Shift + F5, and then select Azure IoT Edge: Stop IoT Edge Simulator from the command palette.

Note

The preceding example shows how to debug IoT Edge modules on containers. It added exposed ports to your module's container createOptions settings. After debugging your modules, remove these exposed ports to make them production ready.

For modules written in C#, including Azure Functions, this example is based on the debug version of Dockerfile.amd64.debug, which includes the .NET Core command-line debugger (VSDBG) in your container image while building it. After debugging your C# modules, use the Dockerfile without VSDBG to make them production ready.

Debug a module with the IoT Edge runtime

Each module folder contains several Docker files for different container types. Use any file ending with the extension .debug to build your module for testing.

When you debug modules using this method, your modules are running on top of the IoT Edge runtime. The IoT Edge device and Visual Studio Code can run on the same machine, but typically, Visual Studio Code runs on the development machine while the IoT Edge runtime and modules run on another physical machine. To debug from Visual Studio Code:

Set up your IoT Edge device, build your IoT Edge modules with the .debug Dockerfile, and then deploy to the IoT Edge device.
Update launch.json so that Visual Studio Code can attach to the process in a container on the remote machine. You can find this file in the .vscode folder in your workspace, and it updates each time you add a new module that supports debugging.
Use Remote SSH debugging to attach to the container on the remote machine.

Build and deploy your module to an IoT Edge device

In Visual Studio Code, open the deployment.debug.template.json deployment manifest file. The deployment manifest describes the modules to be configured on the targeted IoT Edge device. Before deployment, update your Azure Container Registry credentials and module images with the proper createOptions values. For more information about createOption values, see How to configure container create options for IoT Edge modules.

If you're using an Azure Container Registry to store your module image, add your credentials to the edgeAgent > settings > registryCredentials section in deployment.debug.template.json. Replace myacr with your own registry name in both places and provide your password and Login server address. For example:

"modulesContent": {
"$edgeAgent": {
  "properties.desired": {
    "schemaVersion": "1.1",
    "runtime": {
      "type": "docker",
      "settings": {
        "minDockerVersion": "v1.25",
        "loggingOptions": "",
        "registryCredentials": {
          "myacr": {
            "username": "myacr",
            "password": "<your_azure_container_registry_password>",
            "address": "myacr.azurecr.io"
          }
        }
      }
    },
...

Add or replace the following stringified content to the createOptions value for each system (edgeHub and edgeAgent) and custom module (for example, filtermodule) listed. Change the values if necessary.

"createOptions": "{\"HostConfig\":{\"PortBindings\":{\"5671/tcp\":[{\"HostPort\":\"5671\"}],\"8883/tcp\":[{\"HostPort\":\"8883\"}],\"443/tcp\":[{\"HostPort\":\"443\"}]}}}"

For example, the filtermodule configuration should be similar to:

"filtermodule": {
"version": "1.0",
"type": "docker",
"status": "running",
"restartPolicy": "always",
"settings": {
    "image": "myacr.azurecr.io/filtermodule:0.0.1-amd64",
    "createOptions": "{\"HostConfig\":{\"PortBindings\":{\"5671/tcp\":[{\"HostPort\":\"5671\"}],\"8883/tcp\":[{\"HostPort\":\"8883\"}],\"443/tcp\":[{\"HostPort\":\"443\"}]}}}"
}

In the Visual Studio Code command palette, run the command Azure IoT Edge: Build and Push IoT Edge solution.
Select the deployment.debug.template.json file for your solution.
In the Azure IoT Hub > Devices section of the Visual Studio Code Explorer view, right-click the IoT Edge device name for deployment and then choose Create Deployment for Single Device.

Tip

To confirm that the device you've chosen is an IoT Edge device, select it to expand the list of modules and verify the presence of $edgeHub and $edgeAgent. Every IoT Edge device includes these two modules.
Navigate to your solution's config folder, select the deployment.debug.amd64.json file, and then select Select Edge Deployment Manifest.

Check your container status from your device or virtual machine by running the docker ps command in a terminal. You should see your container listed after running the command. If Visual Studio Code and the IoT Edge runtime run on the same machine, check the status in the Visual Studio Code Docker view.

Important

If you're using a private registry like Azure Container Registry for your images, you may need to authenticate to push images. Use docker login <Azure Container Registry login server> or az acr login --name <Azure Container Registry name> to authenticate.

Provide your container registry credentials to Docker so that it can push your container image to storage in the registry.

Sign in to Docker with the Azure Container Registry credentials that you saved after creating the registry.
```
docker login -u <Azure Container Registry username> -p <Azure Container Registry password> <Azure Container Registry login server>
```
You might receive a security warning recommending the use of --password-stdin. While it's a recommended best practice for production scenarios, it's outside the scope of this tutorial. For more information, see the docker login reference.
Sign in to the Azure Container Registry. You may need to Install Azure CLI to use the az command. This command asks for your user name and password found in your container registry in Settings > Access keys.
```
az acr login -n <Azure Container Registry name>
```

Tip

If you get logged out at any point in this tutorial, repeat the Docker and Azure Container Registry sign in steps to continue.

Build module Docker image

Use the module's Dockerfile to build the Docker image.

docker build --rm -f "<DockerFilePath>" -t <ImageNameAndTag> "<ContextPath>"

For example, to build the image for the local registry or an Azure Container Registry, use the following commands:

# Build the image for the local registry

docker build --rm -f "./modules/filtermodule/Dockerfile.amd64.debug" -t localhost:5000/filtermodule:0.0.1-amd64 "./modules/filtermodule"

# Or build the image for an Azure Container Registry

docker build --rm -f "./modules/filtermodule/Dockerfile.amd64.debug" -t myacr.azurecr.io/filtermodule:0.0.1-amd64 "./modules/filtermodule"

Push module Docker image

Push your module image to the local registry or a container registry.

docker push <ImageName>

For example:

# Push the Docker image to the local registry

docker push localhost:5000/filtermodule:0.0.1-amd64

# Or push the Docker image to an Azure Container Registry
az acr login --name myacr
docker push myacr.azurecr.io/filtermodule:0.0.1-amd64

Deploy the module to the IoT Edge device

Use the IoT Edge Azure CLI set-modules command to deploy the modules to the Azure IoT Hub. For example, to deploy the modules defined in the deployment.debug.template.json file to IoT Hub my-iot-hub for the IoT Edge device my-device, use the following command:

az iot edge set-modules --hub-name my-iot-hub --device-id my-device --content ./deployment.debug.template.json --login "HostName=my-iot-hub.azure-devices.net;SharedAccessKeyName=iothubowner;SharedAccessKey=<SharedAccessKey>"

Tip

You can find your IoT Hub shared access key in the Azure portal in your IoT Hub > Security settings > Shared access policies > iothubowner.

Debug your module

To debug modules on a remote device, use Remote SSH debugging in Visual Studio Code.

Enable Visual Studio Code remote debugging by installing the Remote Development extension. For more information about Visual Studio Code remote debugging, see Visual Studio Code Remote Development.

For details about using Remote SSH debugging in Visual Studio Code, see Remote Development using SSH.

In the Visual Studio Code Debug view, select the debug configuration file for the module. By default, the .debug Dockerfile, module's container createOptions settings, and the launch.json file use localhost.

Select Start Debugging or F5, and then select the process to attach to. In the Visual Studio Code Debug view, you see variables in the left panel.

Debug using Docker remote SSH

The Docker and Moby engines support SSH connections to containers allowing you to debug in Visual Studio Code connected to a remote device. You need to meet the following prerequisites before you can use this feature.

Remote SSH debugging prerequisites might differ depending on the language you use. The following sections describe the setup for .NET. For information on other languages, see Remote Development using SSH for an overview. Details about how to configure remote debugging are included in debugging sections for each language in the Visual Studio Code documentation.

Configure Docker SSH tunneling

Follow the steps in Docker SSH tunneling to set up SSH tunneling on your development computer. SSH tunneling requires public/private key pair authentication and a Docker context defining the remote device endpoint.
Connecting to Docker requires root privileges. Follow the steps in Manage docker as a non-root user to allow connection to the Docker daemon on the remote device. When you finish debugging, you might want to remove your user from the Docker group.
In Visual Studio Code, use the Command Palette (Ctrl+Shift+P) to issue the Docker Context: Use command to activate the Docker context pointing to the remote machine. This command lets both Visual Studio Code and Docker CLI use the remote machine context.

Tip

All Docker commands use the current context. Remember to change context back to default when you are done debugging.

To verify the remote Docker context is active, list the running containers on the remote device:

docker ps

The output lists the containers running on the remote device, similar to the following:

PS C:\> docker ps        
CONTAINER ID   IMAGE                                                             COMMAND                   CREATED        STATUS         PORTS                                                                                                                                   NAMES
a317b8058786   myacr.azurecr.io/filtermodule:0.0.1-amd64                         "dotnet filtermodule…"    24 hours ago   Up 6 minutes                                                                                                                                           filtermodule
d4d949f8dfb9   mcr.microsoft.com/azureiotedge-hub:1.5                            "/bin/sh -c 'echo \"$…"   24 hours ago   Up 6 minutes   0.0.0.0:443->443/tcp, :::443->443/tcp, 0.0.0.0:5671->5671/tcp, :::5671->5671/tcp, 0.0.0.0:8883->8883/tcp, :::8883->8883/tcp, 1883/tcp   edgeHub
1f0da9cfe8e8   mcr.microsoft.com/azureiotedge-simulated-temperature-sensor:1.0   "/bin/sh -c 'echo \"$…"   24 hours ago   Up 6 minutes                                                                                                    
                                       tempSensor
66078969d843   mcr.microsoft.com/azureiotedge-agent:1.5                          "/bin/sh -c 'exec /a…"    24 hours ago   Up 6 minutes                                                                                                    
                                       edgeAgent

In the .vscode directory, open launch.json in Visual Studio Code and add a new configuration. Select Add configuration, and then choose the matching remote attach template for your module. For example, the following configuration is for .NET Core. Change the value for the -H parameter in PipeArgs to your device DNS name or IP address.

"configurations": [
{
  "name": "Remote Debug IoT Edge Module (.NET Core)",
  "type": "coreclr",
  "request": "attach",
  "processId": "${command:pickRemoteProcess}",
  "pipeTransport": {
    "pipeProgram": "docker",
    "pipeArgs": [
      "-H",
      "ssh://[email protected]:22",
      "exec",
      "-i",
      "filtermodule",
      "sh",
      "-c"
    ],
    "debuggerPath": "~/vsdbg/vsdbg",
    "pipeCwd": "${workspaceFolder}",
    "quoteArgs": true
  },
  "sourceFileMap": {
    "/app": "${workspaceFolder}/modules/filtermodule"
  },
  "justMyCode": true
},

Remotely debug your module

In Visual Studio Code Debug view, select the debug configuration Remote Debug IoT Edge Module (.NET Core).
Select Start Debugging or select F5. Select the process to attach to.
In the Visual Studio Code Debug view, you see the variables in the left panel.
In Visual Studio Code, set breakpoints in your custom module.
When a breakpoint is hit, you can inspect variables, step through code, and debug your module.

Note

The preceding example shows how to debug IoT Edge modules on remote containers. The example adds a remote Docker context and changes to the Docker privileges on the remote device. After you finish debugging your modules, set your Docker context to default and remove privileges from your user account.

See this IoT Developer blog entry for an example using a Raspberry Pi device.

Next steps

After you build your module, learn how to deploy Azure IoT Edge modules.

To develop modules for your IoT Edge devices, learn about and use Azure IoT Hub SDKs.

Share via

Debug Azure IoT Edge modules using Visual Studio Code

Prerequisites

Debug without a container using the IoT Edge simulator

Debug in attach mode using IoT Edge simulator

Debug a module with the IoT Edge runtime

Build and deploy your module to an IoT Edge device

Sign in to Docker

Build module Docker image

Push module Docker image

Deploy the module to the IoT Edge device

Debug your module

Debug using Docker remote SSH

Configure Docker SSH tunneling

Remotely debug your module

Next steps

Feedback

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